Japanese patent publication No. 3605343 proposes an access control system in which proxy server 1 having first database 8 and second database 9 controls access by client computer 5 to a site. First database 8 stores URLs of sites to which access is permitted, and second database 9 stores URLs of sites to which access is inhibited.
Specifically, proxy server 1 receives from client computer 5 a URL of a site to be accessed, and checks which of the databases the URL is registered in. As a result of the check, if the URL is registered in first database 8, proxy server 1 permits access by client computer 5 to the site, and if it is registered in second database 9, inhibits access to the site.
Similarly, unexamined Japanese patent publication No. 2002-73548 proposes an access control system in which router 10 storing URLs of harmful sites and URLs of harmless sites controls access by a terminal device to a site. Alternatively, unexamined Japanese patent publication No. 2002-24110 proposes an access control system where HUB 100 having an access-inhibit URL list controls access by PC 200 to a site.